Dose response association of pregnancy cigarette smoke exposure, childhood stature, overweight and obesity

Background: The combined dose response effects of pregnancy cigarette smoke exposure on childhood overweight, obesity and short stature have not been reported. Method: A community based cross-sectional survey of 3038 children aged 5–11 years from 15 primary schools in Merseyside, UK. Self-completed parental questionnaires were used for family characteristics, socio-economic status and parental smoking practices. Children were measured for height and weight and z-scores calculated for parental smoking categories. Results: Of 689 (34.0%) mothers who smoked during pregnancy 50.5% smoked ten or more cigarettes daily (heavy smokers). Children of maternal non-smokers had prevalence estimates for overweight, obesity and short stature of 25, 9.6 and 3.2%, respectively. Prevalence estimates were higher in children of mothers who were heavy smokers during pregnancy, 31.5% (P = 0.001), 15.6% (P < 0.001) and 5.5% (P = 0.001), respectively. Mean height for age z-scores was lower among heavy maternal (P < 0.001) and paternal smokers (P < 0.01) compared to non-smokers. Childhood overweight, obesity or short stature were all associated with heavy maternal smoking during pregnancy (all P < 0.001). Mean body mass index (BMI) z-scores were higher in boys of mothers who smoked (P = 0.043). The adjusted odds ratio for short stature in children of heavy maternal smokers was 2.76 (95% CI 1.21–6.33) and 4.28 (1.37–13.37) if both parents were heavy smokers. The adjusted OR for obesity in children of maternal smokers was 1.61(1.19–2.18). The population attributable risk for short stature was 8.8% (1.1–22.7) for heavy maternal smokers. Conclusion: A dose-response association was observed between pregnancy smoking exposure, short stature and obesity.